Index for Section 3

Alphabetical listing for G

Bottom of page

gethostbyname(3)
NAME
  gethostbyname, gethostbyname_r - Get a network host entry by name

SYNOPSIS
  #include <netdb.h>

  struct hostent *gethostbyname(
	  const char *name );

  [Tru64 UNIX]	The following function is supported in order to maintain
  backward compatibility with previous versions of the operating system.  You
  should not use it in new designs.

  int gethostbyname_r(
	  const char *name,
	  struct hostent *hptr,
	  struct hostent_data *hdptr );

LIBRARY
  Standard C Library (libc)

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  gethostbyname():  XNS4.0, XNS5.0

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

PARAMETERS
  name
      Specifies the official network name or alias.

  hptr
      [Tru64 UNIX]  For gethostbyname_r() only, this points to the hostent
      structure.  The netdb.h header file defines hostent structure.

  hdptr
      [Tru64 UNIX]  For gethostbyname_r() only, this is data for hosts
      database.	 The netdb.h header file defines hostent_data structure.

DESCRIPTION
  The gethostbyname() function returns a pointer to a structure of type
  hostent.  Its members specify data obtained from either the local
  /etc/hosts file or one of the files distributed by DNS/BIND or NIS. To
  determine which file or files to search, and in which order, the system
  uses the switches in the /etc/svc.conf file.	The netdb.h header file
  defines the hostent structure.

  If using DNS/BIND, the information is obtained from a name server specified
  in the /etc/resolv.conf file.

  If the name parameter does not contain a dot "." and you are using
  DNS/BIND, the gethostbyname() function checks whether the environment
  variable HOSTALIASES is set.	If set, it first searches the file named by
  HOSTALIASES for an alias matching the name parameter.	 The alias file has
  the following format:

       name1 name2

  name1
      The alias name.  This name cannot include dots.

  name2
      The host name used by DNS/BIND to look up the host information.  The
      hosts database must be distributed by DNS/BIND.

NOTES
  The gethostbyname() function returns a pointer to thread-specific data.
  Subsequent calls to this or a related function from the same thread
  overwrite this data.

  [Tru64 UNIX]	The gethostbyname_r() function is an obsolete reentrant
  version of the gethostbyname() function.  It is supported in order to
  maintain backward compatibility with previous versions of the operating
  system and should not be used in new designs.	 Note that you must zero-fill
  the hdptr structure before its first access by the gethostbyname_r()
  function.

RETURN VALUES
  Upon successful completion, the gethostbyname() function returns a pointer
  to a hostent structure.  If it reaches the end of the network host name
  database, it returns a null pointer.

  [Tru64 UNIX]	Upon successful completion, the gethostbyname_r() function
  stores the hostent structure in the location pointed to by hptr, and
  returns a value of 0 (zero). Upon failure, it returns a value of -1.

ERRORS
  If the gethostbyname() or gethostbyname_r() function call fails, h_errno is
  set to one of the following the values:

  [HOST_NOT_FOUND]
      Host is unknown.

  [NO_DATA]
      The server recognized the request and the name, but no address is
      available for the name.  Another type of name server request may be
      successful.

  [NO_RECOVERY]
      An unexpected server failure occurred.  This is a nonrecoverable error.

  [TRY_AGAIN]
      A transient error occurred, for example, the server did not respond.  A
      retry at some later time may be successful.

  [Tru64 UNIX]	If any of the following conditions occurs, the
  gethostbyaddr_r() function sets errno to the corresponding value:

  [EINVAL]
      The name, hptr, or hdptr is invalid.

FILES
  /etc/hosts
      The Internet network host name database. Each record in the file
      occupies a single line and has three fields consisting of the host
      address, official host name, and aliases.

  /etc/resolv.conf
      The resolver configuration file.

  /etc/svc.conf
      The database service selection configuration file.

SEE ALSO
  Functions: endhostent(3), gethostbyaddr(3), sethostent(3).

  Files: hostname(5), resolv.conf(4), svc.conf(4).

  Networks: bind_intro(7), nis_intro(7).

  Standards: standards(5)

  Network Programmer's Guide

Index for Section 3

Alphabetical listing for G

Top of page